From 0ab4afbf4236e6823be6b8845b7e9fa77f7c61f9 Mon Sep 17 00:00:00 2001
From: Isaac Hier <isaachier@gmail.com>
Date: Thu, 21 Jun 2018 08:14:26 -0400
Subject: [PATCH 1/3] Fix increment operation for bigint -1

---
 src/bigint.cpp | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/bigint.cpp b/src/bigint.cpp
index 367ae79b6c..088703402d 100644
--- a/src/bigint.cpp
+++ b/src/bigint.cpp
@@ -1683,10 +1683,20 @@ void bigint_incr(BigInt *x) {
         bigint_init_unsigned(x, 1);
         return;
     }
-    
-    if (x->digit_count == 1 && x->data.digit != UINT64_MAX) {
-        x->data.digit += 1;
-        return;
+
+    if (x->digit_count == 1) {
+        if (x->is_negative) {
+            if (x->data.digit != 0) {
+                x->data.digit -= 1;
+            }
+            return;
+        }
+        else {
+            if (x->data.digit != UINT64_MAX) {
+                x->data.digit += 1;
+            }
+            return;
+        }
     }
 
     BigInt copy;

From eeda1a1396eb2732e8fe9234bd13d21ac334cfac Mon Sep 17 00:00:00 2001
From: Isaac Hier <isaachier@gmail.com>
Date: Thu, 21 Jun 2018 08:17:08 -0400
Subject: [PATCH 2/3] Fix logic

---
 src/bigint.cpp | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/src/bigint.cpp b/src/bigint.cpp
index 088703402d..bb227a7c3d 100644
--- a/src/bigint.cpp
+++ b/src/bigint.cpp
@@ -1685,16 +1685,11 @@ void bigint_incr(BigInt *x) {
     }
 
     if (x->digit_count == 1) {
-        if (x->is_negative) {
-            if (x->data.digit != 0) {
-                x->data.digit -= 1;
-            }
+        if (x->is_negative && x->data.digit != 0) {
+            x->data.digit -= 1;
             return;
-        }
-        else {
-            if (x->data.digit != UINT64_MAX) {
-                x->data.digit += 1;
-            }
+        } else if (!x->is_negative && x->data.digit != UINT64_MAX) {
+            x->data.digit += 1;
             return;
         }
     }

From f1207a8e744617d62e5c535cf05764cdf2cfd99e Mon Sep 17 00:00:00 2001
From: Isaac Hier <isaachier@gmail.com>
Date: Thu, 21 Jun 2018 08:32:05 -0400
Subject: [PATCH 3/3] Add test case

---
 test/behavior.zig        |  1 +
 test/cases/bugs/1111.zig | 12 ++++++++++++
 2 files changed, 13 insertions(+)
 create mode 100644 test/cases/bugs/1111.zig

diff --git a/test/behavior.zig b/test/behavior.zig
index 096c07b2e0..b494c623e2 100644
--- a/test/behavior.zig
+++ b/test/behavior.zig
@@ -13,6 +13,7 @@ comptime {
     _ = @import("cases/bugs/656.zig");
     _ = @import("cases/bugs/828.zig");
     _ = @import("cases/bugs/920.zig");
+    _ = @import("cases/bugs/1111.zig");
     _ = @import("cases/byval_arg_var.zig");
     _ = @import("cases/cast.zig");
     _ = @import("cases/const_slice_child.zig");
diff --git a/test/cases/bugs/1111.zig b/test/cases/bugs/1111.zig
new file mode 100644
index 0000000000..51ce90af52
--- /dev/null
+++ b/test/cases/bugs/1111.zig
@@ -0,0 +1,12 @@
+const Foo = extern enum {
+    Bar = -1,
+};
+
+test "issue 1111 fixed" {
+    const v = Foo.Bar;
+
+    switch(v) {
+    Foo.Bar => return,
+    else => return,
+    }
+}